An international team of researchers has analyzed the ancient DNA of nearly 300 people in the Iberian Peninsula, covering a period of more than 12,000 years, in two studies published today in Current biology and Science. The first study focused on hunter-gatherers and the first farmers living in the Iberian Peninsula between 13,000 and 6,000 years old. The second examined individuals from the area during all periods over the last 8,000 years. Together, the two articles greatly increase our knowledge of the history of the people of this unique region.

The Iberian Peninsula has long been considered a special case of the history of the European population, because of its unique climate and its position in the far west of the continent. During the last ice age, Iberia remained relatively warm, allowing plants and animals – and eventually people – who were forced to retreat from much of the rest of Europe to continue to live there. Likewise, over the past 8,000 years, Iberia's geographical location, its rugged terrain, its position on the Mediterranean coast and its proximity to North Africa made it unique compared to other parts of the country. Europe in its interactions with other regions. Two new studies, published simultaneously in Current biology and Science, analyze a total of nearly 300 people who lived between 13 000 and 400 years to give an unprecedented clarity on the unique history of the population of the Iberian Peninsula.

A man and a woman buried side by side on the Castillejo de Bonete site in Spain, in the Bronze Age, had different genetic origins. (Luis Benítez de Lugo Enrich and José Luis Fuentes Sánchez / Oppida )

Iberian hunter-gatherers show two ancient Paleolithic lineages

For paper Current biology, Under the direction of researchers from the Max Planck Institute for the Science of Human History, researchers analyzed 11 hunter-gatherers and Neolithic individuals from the Iberian Peninsula. The oldest newly analyzed individuals are about 12,000 years old and were recovered from Balma Guilanyà in Spain.

Earthworks underway on the Balma Guilanyà site. ( CEPAP-UAB)

Previous evidence had shown that after the last ice age, ancestral hunter-gatherers associated with a person of about 14,000 years of age in Villabruna, Italy, dominated Western Europe . It is thought that Italy has been a potential refuge for humans during the last ice age, like Iberia. Villabruna-related ancestry has largely replaced the earlier ancestry in Western and Central Europe related to individuals aged 19,000 to 15,000 associated with what is known as the Magdalenian cultural complex.

Interestingly, the results of the current study show that both lineages were present in Iberian individuals as far back as 19,000 years ago. "We can confirm the survival of another Paleolithic lineage that dates back to the end of the Iberian ice age," said Wolfgang Haak of the Max Planck Institute for the Science of Human History, lead author of the study. "This confirms the role of the Iberian Peninsula as a refuge during the last glacial maximum, not only for the fauna and flora, but also for the human populations."

Prehistoric hunter-gatherers. ( CC0)

This suggests that, far from being replaced by individuals related to Villabruna after the last ice age, the hunter-gatherers of Iberia actually had ancestors from sources related to the Magdalenian and Villabruna. The discovery suggests an early connection between two potential refugees, resulting in a genetic ancestry that has survived in Iberian hunter-gatherers.

"The hunter-gatherers of the Iberian Peninsula carry a mixture of two older types of genetic ancestry: one that dates back to the last glacial maximum and that was once maximized in individuals attributed to the Magdalenian culture and the Another which is found everywhere in the west and the center of the country.Europe replaced the Magdalenian lineage at the beginning of the Holocene, except in the Iberian peninsula ", explains Vanessa Villalba-Mouco of the Max Planck Institute for the Science of Human History, first author of the study.

The researchers hope that ongoing efforts to decipher the genetic structure of hunter-gatherer groups in Europe will contribute to a better understanding of Europe's past and, in particular, to the assimilation of a Neolithic lifestyle created by expanding farmers in the Near East during the year. l & # 39; Holocene.

The old DNA of individuals covering the last 8,000 years helps clarify the history and prehistory of the Iberian Peninsula

The article published in Science focuses on slightly later time periods and traces the history of the Iberian population over the last 8,000 years by analyzing the ancient DNA of a large number of people. ;people. The study, led by the Harvard Medical School and the Broad Institute and comprising Haak and Villalba-Mouco, analyzed 271 Iberians from Mesolithic, Neolithic, Copper Age ancestry , iron age and historical periods. The large number of individuals allowed the team to make more detailed inferences about each period than before.

These two skeletons in La Braña, in northwestern Spain, belonged to black-haired, blue-eyed brothers who lived 8,000 years ago and who were closely linked to the hunter-gatherers of the land. ;Central Europe. ( Julio Manuel Vida Encinas )

The researchers found that during the transition to a sedentary farming lifestyle, Iberia hunter-gatherers subtly contributed to the genetic makeup of newly arrived farmers in the Near East. "We can see that there has to be a local mix because Iberian farmers also carry this double signature of unique hunter-gatherer ancestry to Iberia," says Villalba-Mouco.

Between 2500 and 2000 BC AD about, the researchers observed the replacement of 40% of Iberia's ancestors and almost 100% of its Y chromosomes by ascendants of the Pontic Steppe, the region of the 39th century. current Ukraine and Russia. It is interesting to note that the results show that, in the Iron Age, "steppe ancestry" had spread not only in the Indo-European regions of the Iberian Peninsula, but also in non-Indo-European regions , such as the region inhabited by Basque people. The researchers' analysis suggests that the current Basques look very much like a typical population of the Iberian Iron Age, including the influx of "steppe ancestry," but that they have not been affected by genetic contributions which affected the rest of the Iberian Peninsula. This suggests that Basque speakers have been genetically affected in the same way as other groups by the arrival of steppe populations, while maintaining their language. It was only after this period that they isolated themselves relatively genetically from the rest of the Iberian Peninsula.

In addition, researchers examined historical periods, including periods of existence of Greek and later Roman colonies in Iberia. The researchers found that, from at least Roman times, the peninsula's ancestry was transformed by the gene flow of North Africa and the eastern Mediterranean. They found that the Greek and Roman colonies tended to be fairly multiethnic, with inhabitants of the center and east of the Mediterranean and North Africa, as well as local inhabitants, and that these interactions had lasting demographic and cultural impacts.

"Beyond the specific knowledge on the Iberian Peninsula, this study shows how a high resolution old DNA transect continuing over historical periods can be used to provide a detailed description of the formation of current populations", explains Haak. "We hope that the future use of similar strategies will provide equally useful information in other parts of the world."

Top Image: Farmers of the Pontic Steppe radically transformed Iberian DNA 4500 years ago. Source: Out of the woods

The article, originally titled " The diversity of the genetic history of the Iberian Peninsula revealed by the double study w as published for the first time in Science Daily.

Source: Max Planck Institute for the Science of Human History. "Unique diversity of the genetic history of the Iberian Peninsula revealed by double studies." ScienceDaily. ScienceDaily, March 14, 2019. www.sciencedaily.com/releases/2019/03/190314151551.htm